Alcohol alkoxylates, which are also known as alkyl polyglycol ethers, are compounds which have been known for decades and which are obtained by reacting alcohols with ethylene oxide and/or propylene oxide. The reaction takes place at elevated temperatures and pressures in the presence of acidic or alkaline catalysts. The use of basic compounds of the alkali and alkaline earth metals is of particular practical significance for the alkoxylation of fatty alcohols. Suitable basic compounds are alkali metal and alkaline earth metal alkoxylates, such as sodium methylate and potassium methylate, or alkali metal and alkaline earth metal hydroxides, such as sodium hydroxide and potassium hydroxide. Recently, alkali metal and alkaline earth metal hydroxides have preferably been used as basic catalysts because, where alkali metal and alkaline earth metal alkoxylates are used, organic solvents, such as methanol, are essential. By contrast, where the alkali metal and alkaline earth metal hydroxides are used, the reaction gives good yields, even in aqueous medium.
However, where aqueous solutions of alkali metal and alkaline earth metal hydroxides are used as basic catalysts, products with unfavorable low-temperature behavior which often tend to precipitate, even at room temperature, are obtained, particularly in the ethoxylation of the fatty alcohols. This is attributable inter alia to the fact that the presence of aqueous solutions of alkali metal and alkaline earth metal hydroxides promotes the formation of high molecular weight polyethylene glycols as secondary products. Although, in principle, these polyethylene glycols can be removed by extraction with suitable solvents, such as water, this does involve another process step which is very time-consuming and, in addition, cannot be universally applied.
According to the abstract of Japanese patent application 07,303,825 from the Journal CA Selects in: Alkoxylated Oleochemicals, Issue 1996, page 5, published by the American Chemical Society, Columbus, Ohio, No. 124, random adducts of C8-18 alcohols containing 5 to 15 moles of ethylene oxide and 0.3 to 5.0 moles of propylene oxide show improved flow behavior at low temperatures. In the only example cited, lauryl alcohol is reacted with about 9 moles of ethylene oxide and about 2.4 moles of propylene oxide in the presence of potassium hydroxide as basic catalyst, a product with a pour point of 7.5° C. being obtained. However, this product also tends to precipitate in storage at temperatures below 0° C. which is problematical.
The problem addressed by the present invention was to provide fatty alcohol alkoxylates which would show very favorable low-temperature behavior and would not have any tendency to precipitate. The low-temperature behavior would be so pronounced that the products would remain clear liquids even at temperatures below 0° C. so that no precipitation would occur, even in the event of storage at low temperatures. In addition, the products obtained would be readily soluble in cold water so that they would, be suitable for use as surface-active compounds, for example in liquid concentrates of detergents. In addition, the compounds would lend themselves to production in the presence of aqueous solutions of bases.